There is a need for better noninvasive imaging methods to detect and assess the nature of peripheral arterial disease for therapeutic planning and monitoring. With the emergence of angiogenetic agents and stem-cell transplantation as potentially new therapeutic options for patients with severe lower extremity ischemia, the importance of such noninvasive assessment methods is growing. The aim of this research program is to develop and evaluate new magnetic resonance (MR) imaging methods aimed at enabling improved detection and characterization of patients with peripheral arterial disease. These new MR imaging tools include those to assess 1) lower extremity vessel anatomy, 2) global and regional perfusion, and 3) skin anatomy and physiology. The general hypothesis is that a new noninvasive and objective set of tools to characterize vascular anatomy, deep tissue and superficial skin perfusion, and skin morphology will provide a less morbid and more accurate predictor of therapy and outcome in patients with severe peripheral arterial disease. The research design will consist of technical studies leading to clinical studies evaluating the efficacy of these methods. The technical studies will be directed at developing and optimizing the various MR sequences and validating them under controlled situations. The clinical studies will be performed on patients with critical limb ischemia and skin pathology.